diff --git a/Code/Tools/ProjectManager/Source/PythonBindings.cpp b/Code/Tools/ProjectManager/Source/PythonBindings.cpp
index 695479c493..f2fd7cbec5 100644
--- a/Code/Tools/ProjectManager/Source/PythonBindings.cpp
+++ b/Code/Tools/ProjectManager/Source/PythonBindings.cpp
@@ -1356,11 +1356,18 @@ namespace O3DE::ProjectManager
 
     IPythonBindings::ErrorPair PythonBindings::GetErrorPair()
     {
-        AZStd::string detailedString = m_pythonErrorStrings.size() == 1
-            ? ""
-            : AZStd::accumulate(m_pythonErrorStrings.begin(), m_pythonErrorStrings.end(), AZStd::string(""));
+        if (const size_t errorSize = m_pythonErrorStrings.size())
+        {
+            AZStd::string detailedString =
+                errorSize == 1 ? "" : AZStd::accumulate(m_pythonErrorStrings.begin(), m_pythonErrorStrings.end(), AZStd::string(""));
 
-        return IPythonBindings::ErrorPair(m_pythonErrorStrings.front(), detailedString);
+            return IPythonBindings::ErrorPair(m_pythonErrorStrings.front(), detailedString);
+        }
+        // If no error was found
+        else
+        {
+            return IPythonBindings::ErrorPair(AZStd::string("Unknown Python Bindings Error"), AZStd::string(""));
+        }
     }
 
     void PythonBindings::AddErrorString(AZStd::string errorString)
diff --git a/scripts/o3de/o3de/download.py b/scripts/o3de/o3de/download.py
index a7d5b56440..e00fd48601 100644
--- a/scripts/o3de/o3de/download.py
+++ b/scripts/o3de/o3de/download.py
@@ -261,19 +261,19 @@ def is_o3de_object_update_available(object_name: str, downloadable_kwarg_key, lo
 
     return repo_copy_updated_date > local_last_updated_time
 
-def is_o3de_engine_update_available(engine_name: str, local_last_updated: str):
+def is_o3de_engine_update_available(engine_name: str, local_last_updated: str) -> bool:
     return is_o3de_object_update_available(engine_name, 'engine_name', local_last_updated)
 
-def is_o3de_project_update_available(project_name: str, local_last_updated: str):
+def is_o3de_project_update_available(project_name: str, local_last_updated: str) -> bool:
     return is_o3de_object_update_available(project_name, 'project_name', local_last_updated)
 
-def is_o3de_gem_update_available(gem_name: str, local_last_updated: str):
+def is_o3de_gem_update_available(gem_name: str, local_last_updated: str) -> bool:
     return is_o3de_object_update_available(gem_name, 'gem_name', local_last_updated)
 
-def is_o3de_template_update_available(template_name: str, local_last_updated: str):
+def is_o3de_template_update_available(template_name: str, local_last_updated: str) -> bool:
     return is_o3de_object_update_available(template_name, 'template_name', local_last_updated)
 
-def is_o3de_restricted_update_available(restricted_name: str, local_last_updated: str):
+def is_o3de_restricted_update_available(restricted_name: str, local_last_updated: str) -> bool:
     return is_o3de_object_update_available(restricted_name, 'restricted_name', local_last_updated)
 
 def _run_download(args: argparse) -> int:
diff --git a/scripts/o3de/tests/test_project_manager_interface.py b/scripts/o3de/tests/test_project_manager_interface.py
new file mode 100644
index 0000000000..a7f48dd702
--- /dev/null
+++ b/scripts/o3de/tests/test_project_manager_interface.py
@@ -0,0 +1,407 @@
+#
+# Copyright (c) Contributors to the Open 3D Engine Project.
+# For complete copyright and license terms please see the LICENSE at the root of this distribution.
+#
+# SPDX-License-Identifier: Apache-2.0 OR MIT
+#
+#
+
+import pytest
+from unittest.mock import patch
+from inspect import signature
+import pathlib
+
+from o3de import manifest, engine_properties, register, cmake, engine_template, enable_gem, disable_gem, project_properties, repo, download
+
+# If any tests are failing in this, this means the interface Project Manager depends on has changed.
+# This likely means that some Project Manager functionality has been broken.
+# Please ensure that functionality found in o3de/Code/Tools/ProjectManager/Source/PythonBindings.cpp
+# still works with the affected interface before updating the test to the latest interface.
+
+
+# manifest interface
+def test_get_engine_json_data():
+    sig = signature(manifest.get_engine_json_data)
+    assert len(sig.parameters) >= 2
+
+    engine_path = list(sig.parameters.values())[1]
+    assert engine_path.name == 'engine_path'
+    assert engine_path.annotation == str or engine_path.annotation == pathlib.Path
+
+    assert sig.return_annotation == dict
+
+def test_load_o3de_manifest():
+    sig = signature(manifest.load_o3de_manifest)
+
+    assert sig.return_annotation == dict
+
+def test_get_o3de_gems_folder():
+    sig = signature(manifest.get_o3de_gems_folder)
+
+    assert sig.return_annotation == pathlib.Path
+
+def test_get_o3de_projects_folder():
+    sig = signature(manifest.get_o3de_projects_folder)
+
+    assert sig.return_annotation == pathlib.Path
+
+def test_get_o3de_restricted_folder():
+    sig = signature(manifest.get_o3de_restricted_folder)
+
+    assert sig.return_annotation == pathlib.Path
+
+def test_get_o3de_templates_folder():
+    sig = signature(manifest.get_o3de_templates_folder)
+
+    assert sig.return_annotation == pathlib.Path
+
+def test_get_o3de_third_party_folder():
+    sig = signature(manifest.get_o3de_third_party_folder)
+
+    assert sig.return_annotation == pathlib.Path
+
+def test_get_manifest_engines():
+    sig = signature(manifest.get_manifest_engines)
+
+    assert sig.return_annotation == list
+
+def test_get_this_engine_path():
+    sig = signature(manifest.get_this_engine_path)
+
+    assert sig.return_annotation == pathlib.Path
+
+def test_get_registered():
+    sig = signature(manifest.get_registered)
+    assert len(sig.parameters) >= 1
+
+    engine_name = list(sig.parameters.values())[0]
+    assert engine_name.name == 'engine_name'
+    assert engine_name.annotation == str
+
+    assert sig.return_annotation == pathlib.Path
+
+def test_get_engine_gems():
+    sig = signature(manifest.get_engine_gems)
+
+    assert sig.return_annotation == list
+
+def test_get_all_gems():
+    sig = signature(manifest.get_all_gems)
+    assert len(sig.parameters) >= 1
+
+    project_path = list(sig.parameters.values())[0]
+    assert project_path.name == 'project_path'
+    assert project_path.annotation == pathlib.Path
+
+    assert sig.return_annotation == list
+
+def test_get_gem_json_data():
+    sig = signature(manifest.get_gem_json_data)
+    assert len(sig.parameters) >= 3
+
+    parameters = list(sig.parameters.values())
+    gem_path = parameters[1]
+    assert gem_path.name == 'gem_path'
+    assert gem_path.annotation == str or gem_path.annotation == pathlib.Path
+    project_path = parameters[2]
+    assert project_path.name == 'project_path'
+    assert project_path.annotation == str or project_path.annotation == pathlib.Path
+
+    assert sig.return_annotation == dict
+
+def test_get_project_json_data():
+    sig = signature(manifest.get_project_json_data)
+    assert len(sig.parameters) >= 2
+
+    project_path = list(sig.parameters.values())[1]
+    assert project_path.name == 'project_path'
+    assert project_path.annotation == str or project_path.annotation == pathlib.Path
+
+    assert sig.return_annotation == dict
+
+def test_get_manifest_projects():
+    sig = signature(manifest.get_manifest_projects)
+
+    assert sig.return_annotation == list
+
+def test_get_engine_projects():
+    sig = signature(manifest.get_engine_projects)
+
+    assert sig.return_annotation == list
+
+def test_get_template_json_data():
+    sig = signature(manifest.get_template_json_data)
+    assert len(sig.parameters) >= 3
+
+    parameters = list(sig.parameters.values())
+    template_path = parameters[1]
+    assert template_path.name == 'template_path'
+    assert template_path.annotation == str or template_path.annotation == pathlib.Path
+    project_path = parameters[2]
+    assert project_path.name == 'project_path'
+    assert project_path.annotation == str or project_path.annotation == pathlib.Path 
+
+    assert sig.return_annotation == dict
+
+def test_get_templates_for_project_creation():
+    sig = signature(manifest.get_templates_for_project_creation)
+
+    assert sig.return_annotation == list
+
+def test_get_repo_json_data():
+    sig = signature(manifest.get_repo_json_data)
+    assert len(sig.parameters) >= 1
+
+    repo_uri = list(sig.parameters.values())[0]
+    assert repo_uri.name == 'repo_uri'
+    assert repo_uri.annotation == str
+
+    assert sig.return_annotation == dict
+
+def test_get_repo_path():
+    sig = signature(manifest.get_repo_path)
+    assert len(sig.parameters) >= 1
+
+    repo_uri = list(sig.parameters.values())[0]
+    assert repo_uri.name == 'repo_uri'
+    assert repo_uri.annotation == str
+
+    assert sig.return_annotation == pathlib.Path
+
+def test_get_manifest_repos():
+    sig = signature(manifest.get_manifest_repos)
+
+    assert sig.return_annotation == list
+
+# engine_properties interface
+def test_edit_engine_props():
+    sig = signature(engine_properties.edit_engine_props)
+    assert len(sig.parameters) >= 4
+
+    parameters = list(sig.parameters.values())
+    engine_path = parameters[0]
+    assert engine_path.name == 'engine_path'
+    assert engine_path.annotation == pathlib.Path
+    new_name = parameters[2]
+    assert new_name.name == 'new_name'
+    assert new_name.annotation == str
+    engine_version = parameters[3]
+    assert engine_version.name == 'new_version'
+    assert engine_version.annotation == str
+
+    assert sig.return_annotation == int
+
+# register interface
+def test_register():
+    sig = signature(register.register)
+    assert len(sig.parameters) >= 17
+
+    parameters = list(sig.parameters.values())
+    engine_path = parameters[0]
+    assert engine_path.name == 'engine_path'
+    assert engine_path.annotation == pathlib.Path
+    project_path = parameters[1]
+    assert project_path.name == 'project_path'
+    assert project_path.annotation == pathlib.Path
+    gem_path = parameters[2]
+    assert gem_path.name == 'gem_path'
+    assert gem_path.annotation == pathlib.Path
+    template_path = parameters[4]
+    assert template_path.name == 'template_path'
+    assert template_path.annotation == pathlib.Path
+    repo_uri = parameters[6]
+    assert repo_uri.name == 'repo_uri'
+    assert repo_uri.annotation == str
+    default_projects_folder = parameters[8]
+    assert default_projects_folder.name == 'default_projects_folder'
+    assert default_projects_folder.annotation == pathlib.Path
+    default_gems_folder = parameters[9]
+    assert default_gems_folder.name == 'default_gems_folder'
+    assert default_gems_folder.annotation == pathlib.Path
+    default_templates_folder = parameters[10]
+    assert default_templates_folder.name == 'default_templates_folder'
+    assert default_templates_folder.annotation == pathlib.Path
+    default_third_party_folder = parameters[12]
+    assert default_third_party_folder.name == 'default_third_party_folder'
+    assert default_third_party_folder.annotation == pathlib.Path
+    remove = parameters[15]
+    assert remove.name == 'remove'
+    assert remove.annotation == bool
+    force = parameters[16]
+    assert force.name == 'force'
+    assert force.annotation == bool
+
+    assert sig.return_annotation == int
+
+def test_remove_invalid_o3de_projects():
+    sig = signature(register.remove_invalid_o3de_projects)
+
+    assert sig.return_annotation == int
+
+# cmake interface
+def test_get_enabled_gem_cmake_file():
+    sig = signature(cmake.get_enabled_gem_cmake_file)
+    assert len(sig.parameters) >= 2
+
+    project_path = list(sig.parameters.values())[1]
+    assert project_path.name == 'project_path'
+    assert project_path.annotation == str or project_path.annotation == pathlib.Path
+
+    assert sig.return_annotation == pathlib.Path
+
+def test_get_enabled_gems():
+    sig = signature(cmake.get_enabled_gems)
+    assert len(sig.parameters) >= 1
+
+    cmake_file = list(sig.parameters.values())[0]
+    assert cmake_file.name == 'cmake_file'
+    assert cmake_file.annotation == pathlib.Path
+
+    assert sig.return_annotation == set
+
+# engine_template interface
+def test_create_project():
+    sig = signature(engine_template.create_project)
+    assert len(sig.parameters) >= 3
+
+    parameters = list(sig.parameters.values())
+    project_path = parameters[0]
+    assert project_path.name == 'project_path'
+    assert project_path.annotation == pathlib.Path
+    project_name = parameters[1]
+    assert project_name.name == 'project_name'
+    assert project_name.annotation == str
+    template_path = parameters[2]
+    assert template_path.name == 'template_path'
+    assert template_path.annotation == pathlib.Path
+
+    assert sig.return_annotation == int
+
+# enable_gem interface
+def test_enable_gem():
+    sig = signature(enable_gem.enable_gem_in_project)
+    assert len(sig.parameters) >= 4
+
+    parameters = list(sig.parameters.values())
+    gem_path = parameters[1]
+    assert gem_path.name == 'gem_path'
+    assert gem_path.annotation == pathlib.Path
+    project_path = parameters[3]
+    assert project_path.name == 'project_path'
+    assert project_path.annotation == pathlib.Path
+
+    assert sig.return_annotation == int
+
+# disable_gem interface
+def test_disable_gem():
+    sig = signature(disable_gem.disable_gem_in_project)
+    assert len(sig.parameters) >= 4
+
+    parameters = list(sig.parameters.values())
+    gem_path = parameters[1]
+    assert gem_path.name == 'gem_path'
+    assert gem_path.annotation == pathlib.Path
+    project_path = parameters[3]
+    assert project_path.name == 'project_path'
+    assert project_path.annotation == pathlib.Path
+
+    assert sig.return_annotation == int
+
+# project_properties interface
+def test_edit_project_properties():
+    sig = signature(project_properties.edit_project_props)
+    assert len(sig.parameters) >= 11
+
+    parameters = list(sig.parameters.values())
+    proj_path = parameters[0]
+    assert proj_path.name == 'proj_path'
+    assert proj_path.annotation == pathlib.Path
+    new_name = parameters[2]
+    assert new_name.name == 'new_name'
+    assert new_name.annotation == str
+    new_id = parameters[3]
+    assert new_id.name == 'new_id'
+    assert new_id.annotation == str
+    new_origin = parameters[4]
+    assert new_origin.name == 'new_origin'
+    assert new_origin.annotation == str
+    new_display = parameters[5]
+    assert new_display.name == 'new_display'
+    assert new_display.annotation == str
+    new_summary = parameters[6]
+    assert new_summary.name == 'new_summary'
+    assert new_summary.annotation == str
+    new_icon = parameters[7]
+    assert new_icon.name == 'new_icon'
+    assert new_icon.annotation == str
+    replace_tags = parameters[10]
+    assert replace_tags.name == 'replace_tags'
+    assert replace_tags.annotation == str or replace_tags.annotation == list
+
+    assert sig.return_annotation == int
+
+# manifest interface
+def test_refresh_repo():
+    sig = signature(repo.refresh_repo)
+    assert len(sig.parameters) >= 1
+
+    repo_uri = list(sig.parameters.values())[0]
+    assert repo_uri.name == 'repo_uri'
+    assert repo_uri.annotation == str
+
+    assert sig.return_annotation == int
+
+def test_refresh_repos():
+    sig = signature(repo.refresh_repos)
+
+    assert sig.return_annotation == int
+
+def test_get_gem_json_paths_from_cached_repo():
+    sig = signature(repo.get_gem_json_paths_from_cached_repo)
+    assert len(sig.parameters) >= 1
+
+    repo_uri = list(sig.parameters.values())[0]
+    assert repo_uri.name == 'repo_uri'
+    assert repo_uri.annotation == str
+
+    assert sig.return_annotation == set
+
+def test_get_gem_json_paths_from_all_cached_repos():
+    sig = signature(repo.get_gem_json_paths_from_all_cached_repos)
+
+    assert sig.return_annotation == set
+
+# download interface
+def test_download_gem():
+    sig = signature(download.download_gem)
+    assert len(sig.parameters) >= 5
+
+    parameters = list(sig.parameters.values())
+    gem_name = parameters[0]
+    assert gem_name.name == 'gem_name'
+    assert gem_name.annotation == str
+    skip_auto_register = parameters[2]
+    assert skip_auto_register.name == 'skip_auto_register'
+    assert skip_auto_register.annotation == bool
+    force_overwrite = parameters[3]
+    assert force_overwrite.name == 'force_overwrite'
+    assert force_overwrite.annotation == bool
+    download_progress_callback = parameters[4]
+    assert download_progress_callback.name == 'download_progress_callback'
+    # Cannot check annotation type so just check name
+
+    assert sig.return_annotation == int
+
+def test_is_o3de_gem_update_available():
+    sig = signature(download.is_o3de_gem_update_available)
+    assert len(sig.parameters) >= 2
+
+    parameters = list(sig.parameters.values())
+    gem_name = parameters[0]
+    assert gem_name.name == 'gem_name'
+    assert gem_name.annotation == str
+    last_updated = parameters[1]
+    assert last_updated.name == 'local_last_updated'
+    assert last_updated.annotation == str
+
+    assert sig.return_annotation == bool